SEER is an authoritative source of information on cancer incidence and survival in the United States. SEER currently collects and publishes cancer incidence and survival data from population-based cancer registries covering approximately 28 percent of the U.S. population.

Endometrial Cancer and Estrogen - Landmark Studies

The contents of this section were published in 2003 as part of SEER's 30th Anniversary celebration.

A study based solely on data from eight population-based cancer registries indicated a link between endometrial cancer and menopausal estrogen consumption in an analysis 30 years ago. This particular study opened a large field of case-control epidemiological studies based on data-rich surveillance systems.

The study synthesized various pieces of evidence to reveal that, in all eight geographic areas surveyed, incidence rates of endometrial cancer had risen steadily from 1969 to 1973, in some areas as much as 10 percent per year. The increase was examined as a function of age, in general appearing most frequently in middle-aged and older women.

The increased use of estrogens, especially estrogens prescribed for symptoms of menopause and osteoporosis, was associated with endometrial cancer. Evidence of the link included SEER registry data that showed an unmistakable relationship between estrogen consumption and endometrial cancer and animal studies that indicated that estrogen is a stimulator of hyperplasia in endometrial cells.

The epidemiologic methods used in this investigation were novel at the time. Efficient use of available data made it possible to view exposure to exogenous hormones as potentially risky more rapidly than with a cohort study. More recently, the Women's Health Initiative followed a large cohort of women until 2002, with a mean followup of 5.2 years. The findings of this large trial concluded that the combination of estrogen and progestin did not significantly raise the risk of endometrial cancer, but did raise the risk of breast cancer. As hormone therapy changes over time, population-based cancer surveillance systems will need to be vigilant in monitoring these cancers.